The present multi-turn high density coil and fabrication method relates to coils used in electrical and electronic equipment, such as inductors and transformers and, particularly, to coils in use for electrical and electronic devices formed of stacked layers of interconnected conductors.
Windings forming coils for an inductor or a transformer are used in electrical and electronic equipment. Such equipment usually has volume-restricted space requirements thereby requiring that such coils or windings have a low profile.
In order to achieve the low profile and minimal space requirements for such coils, the fill factor of the windings of the coils needs to be maximized so that the maximum amount of current carrying conductors completely a given space.
Planar magnetics i.e., inductors or transformers, has recently gained interest due to performance, space utilization and fabrication efficiency. For planar magnetics, there are three general methods of building coil windings. The first one is a conventional wire winding process, where edgewise winding can be used to make a planar coil. However, this process has limitations in shape or configuration of the end structure. It is further difficult to have tightly wound coils or wide flat coils, especially with edgewise winding, since the coils are processed from thick copper wire.
A second planar magnetic winding technique is to use PCB or semiconductor fabrication processes. The winding structure is built using a metal deposition or plating and etching processes. This fabrication method has a limitation in conductor fill factor which is important to maximize DC performance, since metal thickness is limited. In addition, inter-layer connection parts have to be prepared using additive metallization such as through hole or side metallization to form a coil with a large number of turns. Such additive processes are usually complicated and show poor conductivity.
The third winding fabrication method uses bus bars for single or several winding structures which are machined out of thick copper plate and built into a coil structure by welding or soldering. The problem of bus bar type construction is that it requires not only machining, but also bending, welding, or soldering.